The combined approach to dentofacial deformity using orthodontics and orthognathic surgery can produce dramatic changes in morphology. Increasing numbers of patients are being treated in this way in the United States. Successful post-surgical physiologic adaptation in most patients permits unimpeded speech. However, speech patterns alter somewhat for most patients and some fail to made adequate compensatory adaptations for normal speech. In the absence of quantifiable data on form-function interrelations, individual response will continue to be unpredicatable. This study will relate the morphologic changes which follow from a variety of surgical approaches to the patients' responses. Hypotheses concerning structural change, stability and adaptation will be tested and data obtained which could render existing techniques of speech analysis as useful adjuncts to routine clinical diagnosis and treatment planning for orthognathic surgery.